Modern communication networks, comprising telecommunications and data communications, may incorporate optical signals with electrical signals. For a variety of reasons, one may therefore convert optical signals to electrical signals, or vice versa throughout various stages of a communication network. For example, a termination of a fiber optic trunk line may involve a conversion of its optical signals into electrical signals that subsequently become routed into electrical-based equipment. Afterward, the electrical signals may be converted back to optical signals. Optical transceivers are generally used to convert between electrical and optical signals.
Industry consensus has resulted in optical transceiver modules that meet common electrical, management, and mechanical specifications. Such a module is commonly referred to as a small form-factor pluggable (SFP) module. One newer high-speed variant is commonly referred to as an XFP module.
As data rates grow beyond 10 Gb/sec, positive-intrinsic-negative (PiN) photodiodes used as a photosensor in a receiver portion of transceiver systems are increasingly being replaced by avalanche photodiodes (APD) for improved receiver sensitivity. But using an APD may involve careful finesse of its operating conditions, including drive bias voltage or temperature compensation, for example.
Proposal SFF-8472, Rev 10.3, released Dec. 1, 2007 (available at ftp://ftp.seagate.com/sff), for example, describes an enhanced functions monitoring interface for optical transceivers, which allows real time access to an SFP/XFP module to monitor its operating parameters, such as temperature and component drive currents, just to name a few examples.
Bit error ratio (BER), the result of dividing the number of bit errors by the total number of bits in a stream, may be used to identify the performance of a communications component, such as an optical transceiver, for example. If bit errors exceed desired limits, one may wish to distinguish between the many possible error sources to identify what problems exist and to what degree.